230 DISEASES OF CROP-PLANTS 



Alarming accounts have been published of the destruction 

 caused by this parasite on the Brazilian plantations, and it is 

 regarded as a serious pest of coffee in Guadeloupe and Martinique. 

 The accounts which have appeared from each of these locaHties 

 suggest very strongly that the effects described may be largely 

 due to fungus root diseases, with the symptoms of which they 

 are in close accord. This impression is to some extent borne out 

 by Fawcett's remarks concerning the status of the parasite on 

 coffee in Porto Rico. Although Heterodera is often active 

 there in trees suffering from root disease, no good evidence has 

 been found that the trees are injured by it to any extent, and its 

 presence is not a necessary accompaniment of root disease. 

 The effects of the same parasite on coffee in the German African 

 Colonies were reported to be trifling, and easily balanced by the 

 use of suitable manures. 



Tylenchus coffece Zimm. is a pest of the local variety of 

 coffee in Java. Liberian coffee is immune, and on the newer 

 kinds the occurrence is sporadic and of small importance. The 

 larvae enter the tender roots, and occupy the root system of young 

 plants, causing wilting and death. The species is also reported 

 from Martinique and Sumatra. 



ScLEROTiuM Disease of Liberian Coffee. 



A preliminary account was given in 191 8 by G. Stahel of a 

 disease which had assumed importance on Liberian coffee in 

 Surinam in the previous year. An earlier mention of the affection 

 had been made by Kuyper under the name of Coremium disease. 

 Recently (1921) Stahel has published a full description and has 

 named the parasite Sclerotium coffeicohim. 



On mature leaves the fungus produces brown dead spots, 

 with distinctly marked concentric rings. In continuously 

 humid weather these may expand over the entire leaf. The 

 underside of the spots bears white, spiny outgrowths, 2-4 mm. 

 long, which do not bear spores, but are easily broken off and 

 carried by the wind to other coffee trees, on which they serve 

 to originate new infestations. 



The ripening fruits are similarly attacked, with the pro- 

 duction of concentric-zoned spots, and when dead they are 

 entirely covered with the white spines. On both leaves and 

 berries while still on the tree there may be developed in damp 

 weather brown or orange-brown sclerotia, and these occur in 

 profusion on the fallen berries. In very damp weather a feathery 

 mycelium, on which sclerotia also later appear, is produced 

 on the material lying on the ground. 



Where a cluster of fruit is involved as a whole, the fungus 

 may invade the cushion, and thus inhibit further production. 



The disease ceases to extend with the onset of dry weather. 

 It is supposed that it is again renewed from the sclerotia, but in 



